Mechanical pressure gauge



2 Sheets-Sheet 1 Filed Mayu, 194s l www ,far

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v INVENTOR NICHOLAS T. VOLSK.

BY 2 n .@MWMMM f ATTORNEYS,

Oct. 21, 1941. N yT VOLSK 2,429,248

MECHANICAL PRES SURE G AUGE Filed May 17, 1945 2 Sheets-Sheet 2' FIG. 2. 1

FIG. 3

JNVENTOR. NICHOLAS T. VOLSK` @.YMWMM ATTORNEYS Patented Oct. 21, 1947 UNITED STATES PATENT OFFICE MECHANICAL PRESSURE GAUGE Nicholas T. Volsk, Spring Lake, NLJ;

Application May 171943, Serial No. 487,293

(Cl. '7S-419.)

(Granted under the act of March 3, 1883) as.

amended April 30, 1928; 3-7'0 0': G. 757)" 7 Claims.

The invention described herein may be manufactured andv used by or for the Government for governmental purposes without the payment to me of anyrroyalty thereon.

This invention relates to a mechanical gauge', and" more particularly to. a device for recording. the time-pressure relationships in explosion chambers when an explosivemixture is ignited.

Any. device Vfor measuring rapidly changing, pressures must possess a suicientl'y high natural frequency to. faithfully follow the expected rates. of change `of pressure.v The high frequency is also necessary for preventing an` elastic oscillation of. a system which may take place because of an impactoi a, suddenly applied pressure. At the same time, the device must be sufficiently sensitive to adequately respond to the. anticipated pressure changes..

The relationship between the natural frequency and the sensitivity oi"l a simple mechanical' spring may be observed from the law which governs the natural' frequency of elastically vibrating bodies which reads;

. K frm/.ir-

f=natural frequency of springY inY cycles per sec-- ond'.

where eseinches g==jconstant of gravity, (Sec )AZ If an instrument is to possess high natural ire-l quency, then the. tWo-variables'at ones disposal", namely, the constant of the springend its weight, must. be: very carefullyy proportioned. The spring constant must be made. as high as practicable, and thev weight of the moving parts must be main-V tained at a minimum..

In: most instruments where a highnatural frequency is, desirable, the strains to which the parts are subjected are very small, and the: desired result is obtained by decreasing the size of: all moving parts, and by using' the lightest materials itis possible to use. Good examples of this are oscillograph vibrators, short periodgalvanometers, microphones, piezoelectric gauges, etc.

In the present case, the instrument must withstand ballistic pressure, and steel is the only material the physical properties of which satisfy the requirements. It is impossible, therefore, to

use materials oi low specific. gravitynor.isit. possible. to.,A reduce the dimensions., of. thev moving. parts. below the safety limits.. It. is.v thus. evi'- dent that K,.tl`1ev constant of the sprng.-,.must bel made very high. rllhis .canbe doneonly by stiffening. the spring, and thus. reducing the. elastic,

displacementunder. load.. Atthe same. time any. reduction in the elastic. displacementfor agiven.

load reduces the sensitivity of the instrument. inv

direct proportion.

The invention represents. a mechanical struclture in. whichv the elements. are given such con-` .It is. a. further obiect o. the present invention.

to provi-de a mechanical. gauge, for measuring time-pressure relationships which is. relatively simple in construction,- and admirably adapted to perform its intended'. functions.

These and other objects and. advantages are attained by providing a structure whichincludes a.

pair of'series-connected' elastic members one of which, when subjected to pressure developed in the explosion chamber, functions as a tension spring, and the other as a, compression. spring.-

The combined displacement of the compression spring and ofthe tension` spring is transmitted by a push rod to an optical system, which records,

by means of a. focused. beamV of. light, the time pressure relationships on a lightv sensitive film moving at a uniform and known velocity.

The novel features which I' believe-to be characteristic of my invention are set forth with par- My invention itself, however, both as toits organizationV and method of operation, together with further objects and advantages thereo, may best. be understood by reference to the following description taken in connection withthfe accompanying draw.n

ings in which:

Figure 1 is a longitudinal sectional view of. a time-pressure gauge made in accordance with the present invention.

Figure. 2 is airagmentary sectional view of an explosion chamber showing the` relative location ofthe gauge with respect to the explosion chamber; and

Figure3 shows aperspective view of. a portion o fi oneV form of a. mirror suspension. assembly plosive materials to V-obtain the thermochemical characteristics thereof. The chamber includes a wall 6 of considerable thickness enclosing a space 43-82-4, the irst mentioned bore'part being interiorly threaded. The part 4 constitutes a port at the space l, and the remainder of the bore receives the mechanical gauge of the present invention, generally designated by the reference character 9. The pressure opening 4 exposes a piston head 3| to the port or explosion chamber 'I disposed within the bore 21 in the compression spring 2l, and is relieved peripherally at 28 and 29 leaving a mid-length annular bearing surface 33 in sliding engagement with the bore of the compression-spring 2|. i,

The head 52 of the push rod 26 is suitably secured to the piston head 3l, as by spot-welding.

-.The piston head 3I, the head 52 of the push rod, 7, the wall being provided with a stepped bore through a gas check 3. While amore or less spe- 'Y cic type of explosion .chamber has .been referred to, it is to be understood that the gauge of the present invention is not limited for use in ,connection therewith. The gauge may be used in any manner or with any chamber appropriate for obtaining the desired measuremen The gauge S'comprises a pair of elastic members I0 and II, member IB beinga tension member, and `member II being a compression member` The tension member lll includes a cylin-v drical head I2 and an integral tubular tension spring I3, the spring portion terminating at its lower end in an enlargedslidebearing portion I4, which impartslateral stability to the tension The cylindrical head I2 lts into the spring I3. bore 2, Fig. .2,` andits upper end surface abuts (through a'gas sealing copper washer. 64) the upper end of the bore. The entire gaugeassembly is held in place by a hollow plug I6, threaded at I'I to t the bore 48 into which it is screwed, the upper end of the plugabutting the cylindrical head I2. The outer 'en d of ,theV plug I6 is provided with a nut portion I8 to venable its placement, and a terminal boss 65 for centering a ring 66 revolubly engaged-on. the outer end of the plug. The plug bore I3 freely surrounds the tenand the upper end of the compression spring 2| thus assembled, form part of a single elastic structure having a sliding fit within the bore 20 of the cylindrical head I2, the piston head 3l being .positioned close to the extremity of the head I2 and in proximity to the explosion chamber l. This proximity avoids the interposition between `the explosion chamber and the piston head of 65, is connected to any appropriate mirror sussion spring I3 and slidingly fits the portion I4 for 'In the support thereofyfasV Yabove stated.

The spring AI3 and head I2 are .bored throughout their length to a uniform diameter asat 20,'

the lower portion Vof this bore being threaded at 5l). Bore 2Q holdsat its inner end anv obturator 3 made of soft copper, disposed against a; piston head 3I in the bore, the hollow, tubular compression member II, and an intermost hollow tubular push rod 26, having an enlarged head portion 52 directly under and againstthe piston head 3l. Thecompression member II consists of a tubular spring 2| provided with exterior relieved parts 22 and 23 separated by a mid-length cylindrical bearing surface 24 in sliding engagement with thebore 20 of thetension spring I3, and pro-l vided, at its outer end, with an enlarged threaded portion 25 engaging a corresponding threaded portion 5I! in the end of the bearing portion I4 of the spring I3. By this arrangement, the tension and compression springs I3 and 2l are effectively connected With each other in series so that any tension and compression strain respectively transmitted to one of these members is also transmitted to the other member, and, by utilizing the combined strains of these members as a basis of measurement, the sensitivity of the instrument is determined by the combined sensitivity ofthe tension and compression springs.

The upper end of the compression member 2l is threadedly engaged at l0with the push rod 26 directly below its head'52. The 'push rod V26 is pension depends in part on the distance betweenA pension assembly for photographically recording the movement of the push rod. `A preferred form .v1 of the mirror suspension assembly 32 is shown,

in Figs. 1 and 3 of the drawings and including a mirror 33, its holder 34, and a back block 35 on.. the holder. It includes a mirror pivot assembly devised by E. M. Eden, National Physical Laboratory, England. ics, by Glazelbrook', vol. 3, pp. 625-627.)

plane parallel to the axis of the gauge and opposite ends in the block 35. Spring 36 is lalso set parallel of the push rod. A similar spring 44 is connected between the base 4I and block 35 in a plane normal to that of springs 40-60 midway of the connections of the latter with the base and block.r

This spring 44 extending between the springs 46-60 and equal distances on opposite sides ofi their plane, and being attached rigidly at its extremities to the base 4I and block 35, the latter having a boss 42 thereon for the purpose. The

springs 40 and 60 connect the mirror assembly with the base 4I, Fig. 1.

ing boss 65, the ring 66 being secured to the hol' low plug I6 by means of bolts `64 and 6l. Springs 40, 60, and 44 form the so-called cross springV suspension which responds to the movement of' the push rod by bending.

The magnifying constant of this mirror susthe two planes of the springs which are parallel to the axis of the gauge, i. e.,- the distance be-` tweenY spring 36 and the plane of the springs lill- 66. At the same time the angular displacement of the mirror assembly is proportionalto. the gauge elongation so long as the latterv re-.. nains small in comparison with the distance be- The outer end of the push rod 26, which eX-. tends substantially to theouterj end of the boss (See Dictionary. of Applied Phys- I The L pivot assembly consists of four ilat, steel spring strips. Two spring strips, 40 and 60, Fig. 3, are set with extremities on a base 4I on the collar 66, in a Springs v4I), 6D vand 44.**- form a pivot support assembly for the mirror. All four springs have equalthickness and eiective- 'Iliirez 1in earl' ruespense@v ai niiet: ex'efee ment, it sh ment: s: t

rangeinntasinee no" editie'ai:system using. gears@ canfonn ai single etastic. systemi Witn the gauge.v

. optical there is any defe' it'. amplined-nany'ti" es" `rlong with`Lr the elastic* displacement" the ge. The' mirror. pivot.. asss'zmblyy illust ted'. in this'. specification avoids! the above nientioisred.I defects'f. and; altrisugliv the elastic type" crmirro'r control' is. noti capable er4 furnishingashign armechani'cai advantage (ratio of; the? leverr' arms)' that'. obtainable With the' gears or knife-edge suspension, it is morei'stablgeg. and;- the're-forei. solves.' the mirror assembly probletr'r more satisfactorily than other know-n.' systems.-V

Wfhn'v the gauge i's subjected? to' pressure', thf mirror is: deflected." '.roughfan.` angle, Where an"ir'roidentleaiiE drperc'il of light (noti Shown-) directed at: the'inir'rr is. deflected through angleV proportion'alV to.' the longitudinat movement of tle push.` fod- 26; thus. fa liful'ly recording in ah ampli'ediform the longitudinali movement.' of' the push rod" 2|? on a light" sensitive lni (not shown moving at a knownand constant' velocity,- asisfamiliar in @monographs o'fvarioiis kinds.

The; operation: of tliega'uge.may'I lie-briey 'surnnfia'rined.l as follows: Dc-known quantity of' exp sive? materiared within th'eleiip-lssion en ber 1. They products of explosion exert a rap Isyv changing pressure against the gas" check 3 and the Had f the pirs'til 33|?` which transmits this pressure to themompression spring 2| through the connectionS25-ofi4 thefpush rod'r 26. Thecompression'spring 2| transmits through the' threaded portions 25 and 5|) the pressure exerted on. the piston head 3| tothe tension spring I3 which is held in place lby the cylindrical head I2 and the plug |6. Thus, both the compression and ten--A sion springs; which preferably have equal Crossfsecti-onal areas, are subjected to equal stresses, the compression spring being compressed the tension spring being elongated; In view' of the series conneotionbetween the tension and compression members' and the engagement between the push rod and the piston 311 and compression. member; the 'movement of the push rod will' regist'efthe" combined elastic displacements ofthe. tension and compression members. This linear movement of the push rod is transformed into an angular movement of the mirror by means of the mirror suspension assembly, the mirror rotation deecting a, beam of light focussed on a photosensitive lm moving at a constant and known velocity. The beam of light traces the time pressure curve on the lm.

The advantages of the gauge described in this specification; reside?. ini thea fact. that. the weighty oltheiiovingparts asi beeni'redi'eed tov a large: extention" making: alatmenibers of hollow tubular reduction in-L Weightzraises` tha.- 1: naturalperiodof the-.elastic system.. Moreover;`

by: parting; the: tubularstructurel tothe corn-- poeiitsoftlre gaugeit becomes possible. to utilize the?. elastici' displacements. ofiy 'thel compression.y

The.' compression` member extends.: throught the entirelength of the gauge, and' its; entire length. novi 'contributes to i thefsensitiyit'yfof thegangettn approximately 2.4. times:-` This gain. in.' sensitivity. isi' not accomplished Wholly;- atv the s' expense? or' the? natural: frequency off' the system,

since'therehasbeen a' reduction .in the weight of l tl-iefs'sensitivity.I of the devices;`

the system which offsets the lowering. ory the natural; iretpleneyi becauseof the increased sensitivitin? Therelative elasticities of thetension spring"v and of the compressionisprings may be controlled' by controilirrg.thei1"-'cross-sectionalareas.` When these' areas-' are'. equal, then the stresses in the" springsv are equa-l; Equal stressing enables one to-iuti'lize-the available metalin the springs to an` equal extent.Y

Itisbelieved.` tliatthe constructionI and opera-- tion. of the!disclosedrnechanical gaugey as Well the.' many' advantages thereof Will be. apparent from the foregoing descriptioni It wil-l, theregli: fore; be apparent that while I have shown and sti described my'invention'ina preferred. form; many` changes andmodications may be made Without v departing fromV the. spirit of the invention assoughttorbe' denediin the appended claims.

The member 2|-` being tted Within the one |3f; the tWomay be said tobe in'-v nested relation. The spring |3`v being xedby the head I2v at its inner endathe outer ends ofthe springs |55k and 2.! being screwed together at. 25 and 50- and the end of the spring 2| being. linked to the registering device, thepressure' of an explosion acting` onA the pistonl 2=|= is-'transmitted from end to end of the member 2|y and then back through the spring |3- end to end. to the head l2. forcesioperating. on the piston act longitudinally throughout thellength of the two springs in train., and in consequence they may be. said to be connected in series in this sense.

I claims l. Inia;y device for recording the nearly instantaneous changes pressure developed by the products or. an explosion, a mounting body having arborevv therein,- a tension member anchoredY at one end efr sa-idf body and longitudinally expand-vk able therein, a.v compression` member secured to thefreeend of` said tension member and extending towardsad anchored end of the tension mem-v bei'.y andflongitudinal-ly compressible therein, said tensionV and. compression members being tubular Y and ot equal' cross-sectional area, apiston artension-,and compression members, whereby the former is elongated and the latter is compressed, a push rod engaged at one end with said piston and slidably engaged Within and against said compression member intermediately of the length of the latter, and means engaged with the other end of said push rod for registering the combined elongation and compression of said tension and compression members.

2. A mechanical pressure gauge comprising a Thus the pressure" support, a head engaged fixedly with the support,

a rectilinear cylindrical tensionspring integrally formed with said head, a bore'l of 'uniform diameter being formed through said head and through said tension spring,'a hollow cylinder` compression spring nested within andtted slidf ably toqsaid bore and extending substantiallyv means connected to the push rod outwardly of said support.

3. A mechanical gauge as in claim 2 in which the cross-sectional areaso'i'said tension spring aidsaid compression spring are equal.

4.`A device for recording the nearly instantaneous changes in pressure developed by an explosion in a closed chamber, comprising a main, centrally-bored, externally-threaded plug adapted to be screwed into a threaded hole in said chamber, a centrally-bored head member bearing against the inner end of said plug and having a thin walled tubular tension member projecting therefrom through the bore in said plug, a piston slidable in the bore of said head, a thin walled tubular compression member abutting and extending from said piston through said tension member, said tension and compression members being secured together at their ends distant from the head, the last named ends being guided and slidably supported in the bore of the plug, pressure-indicating means including a movable element mounted outside the plug, and a hollow push rod extending from said piston through said tubular compression member to-said movable element, said push rod, compression member, and tension member being concentrically related and relatively slidable one within the other and having appropriate intermediate bearing surfaces therebetween such that the concentrically-related members serve to mutually stiien and support one another against lateral bending, buckling, or the like.

5. In a device for registering the nearly instantaneous changes in pressure developed by the products of an explosion, including a hollow mount for engagement through 'the'wall of an explosion chamber and open tothe chamber, a pressure-responsive movable member therein exposed to the interior of the chamber arranged to be in close proximity with the wave front of the expanding gases resulting from therexplosion, a register distant from the chamber, an operative connection between the pressure-responsive member and register, a pair of nested and thin-walled tubular compression and tension members of equal cross-sectional area mutually united at their extremities distant from the chamber, relatively slidable at their opposite extremities and connected respectively to the mount and pressure-responsive member to respond by longitudinal strains to the-pressure electsvof-an explosion on said pressure-responsive member,said tubular members being concentrically arranged and relatively slidable one within the other, -the tensiony member being the external one, said operative,

connection having also a part slidingly iitted to the inner of said nested members medially -of its eective length, whereby to-support the same against lateral bending.

6. A device for recording the nearly instan-- taneous changes in pressure developed by an explosion in a closed chambenthe'said device comexternallythreaded plug adapted to be screwed into a threaded hole in said chamber, a centrally boredhead member bearing against the inner end of said plug and having a tubular tension member`- prising` a main, centrally-bored,

projecting therefrom through the bore in said plug, a piston slidable in said head member, a

tubular compression member extending from said piston and said head member and through said tension member, said tension and compression members being secured together at their ends distant from the head, motion registering means including an element mounted outside the p1ug, and a push rod extending from said piston longitudinally through said tubular compression member to said element outside the'plug and having a part tted slidably within and against the compression memberintermediately of the length ofl the latter. y i

7. In a device for recording the nearly instantaneous changes in pressure developed by ex-l to the other tubular member at its other `end whereby to constitute said tubular members tension and compression elements respectively, said push rod and said other tubular element abutting the outward side of the piston for outward urging thereby, and means to maintain' radial spacing between said elements and-between the push rod and the adjacent one of said elements medially of each. i

NICHOLAS T` VOLSK.

REFERENCES CITED The following references are oli'record in the iile of this patent: V

UNITED STATES PATENTS Name Date Thring Nov. 29, 1921 Cutts et al. Feb. I14, 1922 Geyer May 29, 1923 Number FOREIGN PATENTS Number Country Date Geyer Sept. 2, 1924V Germany Mar. 24, 1891 

